Conventional wound-field rotary electric machines include a rotor with a field coil through which a field current flows, and a stator with an armature coil through which an armature current flows. Such a wound-field rotary electric machine is desired to have improved power efficiency. To fulfill this requirement, patent literature 1 described below discloses a control apparatus and a control method for controlling a rotary electric machine. The control apparatus and control method are configured to control the rotary electric machine based on a control map comprised of the combination between the phases of voltages applied to the armature coil and field currents. The control map is designed to minimize power loss.